Mitsubishi Electric HP120TNU-A Service Handbook page 146

[5-2 Outdoor Unit Control ]
(2) Two-outdoor-unit system
Initial startup mode starts.
The compressor on the OC starts up.
F 60Hz
The total operating load of the indoor unit
after 5 minutes of operation is P96 or above.
The compressor on the OC remains in operation, and the
compressor on the OS starts up.
50 F 60Hz (both OC and OS)
Completed in the integrated operation time of 35 minutes.
or F < 50Hz (both OC and OS)
Completed in the integrated operation time of 90 minutes.
or the discharge superheat (TH4 - Tc) is detected (within
5 minutes of startup) that remains above approximately
25 degrees for one minute .
Initial startup mode complete
1 Qj:Total capacity (models) code
For information about capacity codes, refer to the following page(s). [5-1-2 Indoor Unit Switch Functions and Factory Set-
tings]
HWE18220_GB
(*1 Qj 50)
Yes
*2
The air conditioning load is too small for both the OC and the OS to
simultaneously stay in operation.
*3
The air conditioning load is high enough for both OC and OS to
simultaneously stay in operation.
No
The compressor on the OC starts up.
*2
50 F 60Hz (OC)
Completed in the integrated operation time of 35 minutes.
or F < 50Hz (OC)
Completed in the integrated operation time of 90 minutes.
or the discharge superheat (TH4 - Tc) is detected (within
5 minutes of startup) that remains above approximately
*3
25 degrees for one minute .
Both the OC and OS stop.
The startup sequence of the OC and OS is rotated.
The compressor on the OS starts up.
50 F 60Hz (OS)
Completed in the integrated operation time of 35 minutes.
or F < 50Hz (OS)
Completed in the integrated operation time of 90 minutes.
or the discharge superheat (TH4 - Tc) is detected (within
5 minutes of startup) that remains above approximately
25 degrees for one minute .
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